Method of manufacturing ultrasound radiating members for a catheter

ABSTRACT

A method comprises providing a substantially planar slab of piezoelectric material having a top surface. The method further comprises drilling a plurality of holes through the top surface and into the slab. The method further comprises making a plurality of cuts through the top surface and into the slab. The cuts form a plurality of polygons that are generally centered about one of the holes. The method further comprises plating the slab with an electrically conductive material. The method further comprises removing the electrically conductive material from the top surface of the slab. The method further comprises cutting the slab substantially parallel to the top surface.

PRIORITY APPLICATION

This application is a divisional of U.S. patent application Ser. No.10/684,845 (filed 14 Oct. 2003), now U.S. Pat. No. 6,921,371, whichclaims the benefit of U.S. Provisional Patent Application 60/418,400(filed 14 Oct. 2002). Both of these priority applications are herebyincorporated by reference herein in their entirety.

FIELD OF THE INVENTION

The present invention relates generally to ultrasound radiating members,and relates more specifically to ultrasound radiating members configuredfor use in medical applications to enhance the delivery and/or effect ofa therapeutic compound.

BACKGROUND OF THE INVENTION

Several therapeutic and diagnostic applications in the medical field useultrasonic energy. For example, ultrasonic energy can be used to enhancethe delivery and/or effect of various therapeutic compounds. See, forexample, U.S. Pat. Nos. 4,821,740, 4,953,565 and 5,007,438. In someapplications, a catheter delivers ultrasonic energy and a therapeuticcompound to a specific treatment site within the body. Such a cathetertypically includes an ultrasonic assembly for generating the ultrasonicenergy and a delivery lumen for delivering the therapeutic compound tothe treatment site. Using this device, sometimes referred to as an“ultrasonic catheter,” the ultrasonic energy can be applied at thetreatment site to enhance the therapeutic effect and/or the delivery ofthe therapeutic compound.

Ultrasonic catheters have successfully been used to treat human bloodvessels that have become occluded or completely blocked by plaque,thrombi, emboli or other substances that reduce the blood carryingcapacity of the vessel. See, for example, U.S. Pat. No. 6,001,069. Toremove the blockage, solutions containing dissolution compounds can bedelivered directly to the blockage site using an ultrasonic catheter. Inthis design, ultrasonic energy generated by the catheter enhances thedelivery and/or therapeutic effect of the dissolution compounds.

Ultrasonic catheters can also be used to perform gene therapy on anisolated region of a body lumen. For example, as disclosed in U.S. Pat.No. 6,135,976, an ultrasonic catheter can be provided with one or moreexpandable sections for occluding a section of the body lumen. A genetherapy composition can then be delivered to the occluded sectionthrough a delivery lumen. Ultrasonic energy is then delivered to theoccluded section to enhance the entry of the gene therapy compositioninto the cells of the occluded section.

Another use for an ultrasonic catheter is the delivery and activation oflight activated drugs, as disclosed in U.S. Pat. No. 6,176,842.Additionally, ultrasound-enhanced thrombolytic therapy can be used todissolve blood clots in arteries and veins in the treatment ofconditions such as peripheral arterial occlusion and deep veinthrombosis. In such applications, an ultrasonic catheter deliversultrasonic energy into a vessel, where the ultrasonic energy enhancesthrombolysis with agents such as urokinase, tissue plasminogen activator(“TPA”) and others.

SUMMARY OF THE INVENTION

Conventional ultrasonic assemblies include one or more ultrasoundradiating members, which usually have a cylindrical or rectangulargeometry. Cylindrical ultrasound radiating members are often difficultto manufacture and can be subject to mechanical failure. Rectangularultrasound radiating members are easier to manufacture but Applicant hasdetermined that they produce a less radially uniform distribution ofultrasound energy Thus, an ultrasound radiating member having animproved manufacturing process, improved durability and with a moreradially uniform distribution of ultrasound energy has been developed.

In accordance with one embodiment of the present invention, anultrasound radiating member comprising a front face and a rear face.Each face has n sides, wherein n is greater than 4. The ultrasoundradiating member further comprises n faces connecting the sides of thefront and rear faces. The ultrasound radiating member further comprisesa central bore extending from the front face to the rear face.

In accordance with another embodiment of the present invention, anultrasound catheter comprises a tubular member. the ultrasound catheterfurther comprises at least one ultrasound radiating member positionedwith the tubular member. The ultrasound radiating member comprises afront face and a rear face. Each face has n sides, wherein n is greaterthan 4. The ultrasound radiating member further comprises n facesconnecting the sides of the front and rear faces. the ultrasoundradiating member further comprises a central bore extending from thefront face to the rear face. At least a portion of the surfaces of theinner bore and n faces are coated with a conductive material. Theultrasound catheter further comprises a first wire and a second wire.The first wire is connected to the inner bore, and the second wire isconnected to at least one of the n faces.

In accordance with another embodiment of the present invention, a methodfor manufacturing an ultrasonic radiating member comprises providing asheet of piezoelectric material. The method further comprises drilling aplurality of holes into the piezoelectric material. Each hole has aninner surface. The method further comprises making a plurality of cutsinto the sheet. Each cut has a depth less than the depth of the holes.The cuts form an elongate polygon that is generally centered about oneof the holes. The polygon has an outer surface. The method furthercomprises plating at least a portion of the inner and outer surfaceswith a conductive material. The method further comprises cutting abackside from the sheet so as to separate individual elongate polygons.

In accordance with another embodiment of the present invention, anapparatus comprises an elongate ultrasound radiating member having ahollow, cylindrical central core and three or more substantially flatsides. The apparatus further comprises a first cylindrical electrodeapplied to the hollow, cylindrical central core. The apparatus furthercomprises a second electrode applied to at least one of the sides.

In accordance with another embodiment of the present invention, a methodcomprises providing a substantially planar slab of piezoelectricmaterial having a top surface. The method further comprises drilling aplurality of holes through the top surface and into the slab. The methodfurther comprises making a plurality of cuts through the top surface andinto the slab. The cuts form a plurality of polygons that are generallycentered about one of the holes. The method further comprises platingthe slab with an electrically conductive material. The method furthercomprises removing the electrically conductive material from the topsurface of the slab. The method further comprises cutting the slabsubstantially parallel to the top surface.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the ultrasound radiating members disclosedherein, and certain applications therefor, are illustrated in theaccompanying drawings, which are for illustrative purposes only. Thedrawings comprise the following figures, in which like numerals indicatelike parts.

FIG. 1 is a side view of an ultrasonic catheter that is particularlywell-suited for use in small vessels of the distal anatomy.

FIG. 2A is a cross-sectional view of the distal end of the ultrasoniccatheter of FIG. 1.

FIG. 2B is a cross-sectional view of the ultrasonic catheter of FIG. 2Ataken through line 2B-2B.

FIG. 3A is side elevation view of one embodiment of an ultrasoniccatheter which is particularly well-suited for treating long segmentperipheral arterial occlusions, such as those occasionally found in thearteries of the leg.

FIG. 3B is a side elevation view of an inner core configured for usewith the ultrasonic catheter of FIG. 3A.

FIG. 3C is a side elevation view of a modified embodiment of anultrasonic catheter.

FIG. 4A is a cross-sectional view of a distal end of the ultrasoniccatheter of FIG. 3A.

FIG. 4B is a cross-sectional view of a proximal end of the ultrasoniccatheter of FIG. 3A.

FIG. 4C is a cross-sectional view of another modified embodiment of anultrasonic catheter.

FIG. 5A is a side view of the distal end of the ultrasonic catheter ofFIG. 3A.

FIG. 5B is a cross-sectional view of the distal end of the ultrasoniccatheter of FIG. 5A taken through line 5B-5B.

FIG. 5C is a side view of a modified embodiment of the distal end of anultrasonic catheter.

FIG. 5D is a cross-sectional view of the distal end of the ultrasoniccatheter of FIG. 5C taken along line 5D-5D.

FIG. 5E is a side view of another modified embodiment of the distal endof an ultrasonic catheter.

FIG. 5F is a side view yet of another modified embodiment of the distalend of an ultrasonic catheter.

FIG. 6A is a side view of yet another modified embodiment of the distalend of an ultrasonic catheter which includes drug delivery ports ofincreasing size.

FIG. 6B is a cross-sectional view of the distal end of an ultrasoniccatheter wherein the proximal and distal ends are made of differentmaterials.

FIG. 7 is a cross-sectional view of a distal end of an ultrasoniccatheter that includes an integral occlusion device.

FIG. 8A illustrates a wiring diagram for connecting a plurality ofultrasound radiating members in parallel.

FIG. 8B illustrates a wiring diagram for connecting a plurality ofultrasound radiating members in series.

FIG. 8C illustrates a wiring diagram for connecting a plurality ofultrasound radiating members with a common wire.

FIG. 9 a wiring diagram for connecting a plurality of temperaturesensors with a common wire.

FIG. 10 is a block diagram of a feedback control system for use with anultrasonic catheter

FIG. 11A is a cross-sectional view of a treatment site.

FIG. 11B is a side view of the distal end of an ultrasonic catheterpositioned at the treatment site.

FIG. 11C is a cross-sectional view of the distal end of the ultrasoniccatheter of FIG. 11B positioned at the treatment site.

FIG. 11D is a side view of the proximal end of the ultrasonic catheterof FIG. 11B.

FIG. 11E is a cross-sectional view of the distal end of the ultrasoniccatheter of FIG. 11B positioned at the treatment site.

FIG. 11F is a cross-sectional view of the distal end of the ultrasoniccatheter of FIG. 11B positioned at the treatment site showing themovement of the inner core.

FIG. 11G is a side view of the distal end of the ultrasonic catheter ofFIG. 11B positioned at the treatment site.

FIG. 12A is a perspective view of an ultrasound radiating member havingpentagonal front and rear faces.

FIG. 12B is a perspective view of an ultrasound radiating member havinghexagonal front and rear faces.

FIG. 12C is a perspective view of an ultrasound radiating member havingoctagonal front and rear faces.

FIG. 12D is a perspective view of an ultrasound radiating member havingtriangular front and rear faces.

FIG. 12E is a perspective view of an ultrasound radiating member havingrectangular front and rear faces.

FIG. 13 is a perspective view of an ultrasound radiating member havingfirst and second wires connected to inner and outer surfaces,respectively.

FIG. 14 is a perspective view of a sheet of piezoelectric materialperforated with through or blind holes.

FIG. 15A is a plan view of the piezoelectric sheet of FIG. 14 havingbeen cut to produce ultrasound radiating members having a hexagonalgeometry.

FIG. 15B is a plan view of the piezoelectric sheet of FIG. 14 havingbeen cut to produce ultrasound radiating members having a octagonalgeometry.

FIG. 16 is a cross-sectional view of the cut piezoelectric sheet of FIG.15A or 15B.

FIG. 17 is a cross-sectional view of the piezoelectric sheet of FIG. 16,illustrating a method of harvesting individual ultrasound radiatingmembers.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Introduction.

Certain exemplary embodiments described herein relate to ultrasoniccatheters and methods of using ultrasonic catheters. As described above,ultrasonic catheters can be used to enhance the effect and/or deliveryof a therapeutic compound. As used herein, the term “therapeuticcompound” refers, in addition to its ordinary meaning, to drugs,biological macromolecules (including, but not limited to, proteins andnucleic acids), and other pharmacological agents, including combinationsthereof. Exemplary applications of ultrasonic catheters are provided inU.S. Pat. Nos. 5,318,014, 5,362,309, 5,474,531, 5,628,728, 6,001,069,and 6,210,356.

In one exemplary embodiment, an ultrasonic catheter is adapted for usein the treatment of thrombus in the small blood vessels or arteries ofthe human body, such as, for example, the small cerebral arteries. Inanother embodiment, an ultrasonic catheter is adapted for use in thetreatment of thrombus in larger blood vessels or arteries of the humanbody such as those located in the lower leg. In still other embodiments,the ultrasonic catheters disclosed herein can also be used in othertherapeutic applications, such as performing gene therapy (see, forexample, U.S. Pat. No. 6,135,976), activating light activated drugs usedto cause targeted tissue death (see, for example, U.S. Pat. No.6,176,842) and causing cavitation to produce biological effects (see,for example, U.S. Pat. RE36,939). Moreover, such therapeuticapplications may be used in various human tissues, such as other partsof the circulatory system, solid tissues, duct systems and bodycavities. Certain embodiments of the ultrasonic catheters disclosedherein can also be used in other medical applications, such asdiagnostic and imaging applications.

In exemplary embodiments, the ultrasonic catheters disclosed herein canbe used in applications where the ultrasonic energy provides atherapeutic effect by itself. For example, in certain applications,ultrasonic energy can provide and/or reduce stenosis and/or restenosis;tissue ablation, abrasion or disruption; promotion of temporary orpermanent physiological changes in intracellular or intercellularstructures; and/or rupture of micro-balloons or micro-bubbles fortherapeutic compound delivery. See, for example, U.S. Pat. Nos.5,269,291 and 5,431,663. The methods and apparatuses disclosed hereincan also be used in applications that do not require the use of acatheter, such as, enhancement of hyperthermic drug treatment, use ofexternally generated ultrasonic energy to enhance the effect and/ordelivery of a therapeutic compound at a specific site within the body,and use of ultrasonic energy to provide a therapeutic or diagnosticeffect by itself. See, for example, U.S. Pat. Nos. 4,821,740, 4,953,565,5,007,438 and 6,096,000.

The term “ultrasonic energy” is used broadly, and encompasses itsordinary definition, as well as mechanical energy transferred throughlongitudinal pressure or compression waves with a frequency greater thanabout 20 kHz and less than about 20 MHz. In one embodiment, the waveshave a frequency between about 500 kHz and 20 MHz, and in anotherembodiment the waves have a frequency between about 1 MHz and 3 MHz. Inyet another embodiment, the waves have a frequency of about 3 MHz.

The term “catheter” is used broadly, and encompasses its ordinarydefinition, as well as flexible tubes configured to be inserted into abody cavity, duct or vessel.

Overview of a Small Vessel Ultrasonic Catheter.

FIGS. 1, 2A and 2B illustrate an exemplary embodiment of an ultrasoniccatheter 100 that is particularly well-suited for use in small vesselsof the distal anatomy, such as in small neurovascular vessels in thebrain.

As illustrated in FIGS. 1 and 2A, the ultrasonic catheter 100 generallycomprises a multi-component tubular body 102 having a proximal end 104and a distal end 106. The tubular body 102 and other components of thecatheter 100 can be manufactured in accordance with conventionalcatheter manufacturing techniques. Suitable dimensions can be readilyselected based on the dimensions of the treatment site and the desiredpercutaneous access site.

In an exemplary embodiment, the tubular body 102 is elongate andflexible, and comprises an outer sheath 108 (illustrated in FIG. 2A)that is positioned over an inner core 110. For example, in embodimentsparticularly well-suited for small neurovascular vessels, the outersheath 108 can comprise extruded polytetrafluoroethylene (“PTFE”),polyetheretherketone (“PEEK”), polyethylene (“PE”), polymides, braidedpolymides and/or other similar materials. In such embodiments, the outersheath 108 has an outer diameter of approximately 0.039 inches at itsproximal end and between approximately 0.033 and approximately 0.039inches at its distal end. In such embodiments, the outer sheath 108 hasan axial length of approximately 150 centimeters. In other embodiments,the outer sheath 108 can be formed from a braided tubing comprising highor low density polyethylenes, urethanes, nylons, and so forth. Suchconfigurations enhance the flexibility of the tubular body 102. In stillother embodiments, the outer sheath 108 can include a stiffening member(not shown) at the tubular body proximal end 104.

The inner core 110 at least partially defines a central lumen 112, or“guidewire lumen,” which preferably extends through the length of thecatheter 100. The central lumen 112 has a distal exit port 114 and aproximal access port 116. As best illustrated in FIG. 1, the proximalaccess port 116 is defined by therapeutic compound inlet port 117 on aback end hub 118, which is attached to the outer sheath proximal end104. In the exemplary embodiment illustrated in FIG. 1, the back end hub118 is attached to a control box connector 120, which described ingreater detail below.

In an exemplary embodiment, the central lumen 112 is configured toreceive a guidewire (not shown) having a diameter of betweenapproximately 0.010 includes to approximately 0.012 inches. In anexemplary embodiment, the inner core 110 is formed from polymide or asimilar material, which can optionally be braided to increase theflexibility of the tubular body 102.

Referring now to the exemplary embodiment illustrated in FIGS. 2A and2B, the distal end 106 of the tubular body 102 includes an ultrasoundradiating member 124. In the illustrated embodiment, the ultrasoundradiating member 124 comprises an ultrasonic transducer, which converts,for example, electrical energy into ultrasonic energy.

In the embodiment illustrated in FIGS. 2A and 2B, the ultrasoundradiating member 124 is in the shape of a hollow cylinder as isconventional in the prior art. Improved radiating members 124 will bedescribed in FIGS. 12 through 17 below.

The inner core 110 extends through the ultrasound radiating member 124,which is positioned over the inner core 110. The ultrasound radiatingmember 124 can be secured to the inner core 110 in a suitable manner,such as with an adhesive. Extending the core through the member 124advantageously provides enhanced cooling of the ultrasound radiatingmember 124. Specifically, as will be explained in more detail below, atherapeutic compound can be injected through the central lumen 112,thereby providing a heat sink for heat generated by the ultrasoundradiating member 124.

As described above, suitable operating frequencies for the ultrasoundradiating member 124 include, but are not limited to, from about 20 kHzto less than about 20 MHz. In one embodiment, the frequency is betweenabout 500 kHz and about 20 MHz, and in another embodiment the frequencyis between about 1 MHz and about 3 MHz. In yet another embodiment, theultrasonic energy has a frequency of about 3 MHz.

In the exemplary embodiment illustrated in FIGS. 2A and 2B, ultrasonicenergy is generated by supplying electrical power to the ultrasoundradiating member 124. The electrical power can be supplied through thecontroller box connector 120, which is connected to a first electricallyconductive wire 126 and a second electrically conductive wire 128. Asillustrated, the wires 126, 128 extend through the catheter body 102. Insuch embodiments, the wires 126, 128 are secured to the inner core 110,lay along the inner core 110 and/or extend freely in the space betweenthe inner core 110 and the outer sheath 108. In the illustratedarrangement, the first wire 126 is connected to the hollow center of theultrasound radiating member 124, while the second wire 128 is connectedto the outer periphery of the ultrasound radiating member 124. In anexemplary embodiment, the ultrasound radiating member 124 comprises apiezoelectric ceramic oscillator; in other embodiments, the ultrasoundradiating member 124 comprises other similar materials.

In the modified embodiment, the catheter 10 may include more than oneultrasound radiating member 124. In such an embodiment, the ultrasoundradiating members may be electronically connected in series or parallelas described above and in more detail below.

Still referring to the exemplary embodiment illustrated in FIGS. 2A and2B, the distal end of the catheter 100 includes sleeve 130, which isgenerally positioned about the ultrasound radiating member 124. In suchembodiments, the sleeve 130 comprises a material that readily transmitsultrasonic energy. Suitable materials for the sleeve 130 include, butare not limited to, polyolefins, polyimides, polyesters and other lowultrasound impedance materials. Low ultrasound impedance materials arematerials that readily transmit ultrasonic energy with minimalabsorption of the ultrasonic energy. The proximal end of the sleeve 130can be attached to the outer sheath 108 with an adhesive 132. In asimilar manner, the distal end of the sleeve 130 can be attached to acatheter tip 134. In the illustrated arrangement, the tip 134 isgenerally rounded and is also attached to the distal end of the innercore 110.

In an exemplary embodiment, the tubular body 102 is divided into atleast three sections of varying stiffness. The first section, whichincludes the proximal end 104, is generally more stiff than a secondsection, which lies between the proximal end 104 and the distal end 106.This arrangement facilitates the movement and placement of the catheter100 within small vessels. The third section, which includes ultrasoundradiating element 124, is generally stiffer than the second section dueto the presence of the ultrasound radiating element 124.

Stilling referring to the exemplary embodiment illustrated in FIG. 2B,the catheter 100 includes at least one temperature sensor 136 that islocated at or near the distal end of the catheter 100, and near theultrasound radiating member 124. Suitable temperature sensors include,but are not limited to, diodes, thermistors, thermocouples, resistancetemperature detectors (“RTD”), and fiber optic temperature sensors thatuse thermalchromic liquid crystals. In an exemplary embodiment, thetemperature sensors are operatively connected to a control box (notshown) through a control wire that extends through the tubular body 102and back end hub 118, and that is operatively connected to a control boxthrough the control box connector 120. In such embodiments, the controlbox includes a feedback control system, such as the control systemdescribed herein. In an exemplary embodiment, the control box isconfigured to monitor and control the power, voltage, current and phaseof the signal supplied to the ultrasound radiating members 124. Thisconfiguration allows the temperature of the catheter to be monitored andcontrolled.

In an exemplary use, a free end of a guidewire is percutaneouslyinserted into the arterial system at a suitable insertion site. Theguidewire is advanced through the vessels towards a treatment site,which includes, for example, a clot. In an exemplary embodiment, theguidewire is directed through the clot.

The catheter 100 is then percutaneously inserted through the insertionsite and advanced along the guidewire towards the treatment site usingconventional over-the-guidewire techniques. The catheter 100 is advanceduntil the distal end of the catheter 100 is positioned at or within theclot. In a modified embodiment, the catheter distal end includesradiopaque markers to aid in positioning the catheter at the treatmentsite.

The guidewire is then withdrawn from the central lumen 112. Atherapeutic compound solution source (not shown), such as a syringe witha Luer fitting, is attached to the therapeutic compound inlet port 117and the control box connector 120 is connected to the control box. Thus,the therapeutic compound can be delivered through the central lumen 112and the exit port 114 to the clot. Suitable therapeutic compounds fortreating thrombus include, but are not limited to, aqueous solutionscontaining a thrombolytic agent (that is, a clot-dissolving drug), suchas, heparin, urokinase, streptokinase, TPA and BB-10153, which ismanufactured by British Biotech (Oxford, United Kingdom). In otherembodiments, wherein the ultrasonic catheter is not used to remove athrombus, other agents can be delivered through the central lumen. Suchother agents include, but are not limited to, cancer treating drugs,genetic material, light activated drugs, and so forth.

The ultrasound radiating member 124 is activated to deliver ultrasonicenergy through the distal end of the catheter 100 to the treatment site.As mentioned above, suitable frequencies for the ultrasound radiatingmember 124 include, but are not limited to, from about 20 kHz to lessthan about 20 MHz. In one embodiment, the frequency is between about 500kHz and about 20 MHz, and in another embodiment the frequency is betweenabout 1 MHz and about 3 MHz. In yet another embodiment, the ultrasonicenergy has a frequency of about 3 MHz. The therapeutic compound andultrasonic energy can be applied until the clot is partially or entirelydissolved. Once the clot has been dissolved to the desired degree, thecatheter 100 can be withdrawn from the treatment site.

In a modified embodiment, the catheter 100 includes a cooling system forremoving heat generated by the ultrasound radiating member 124. In onesuch embodiment, a return path can be formed in region 138, such thatcoolant from a coolant system can be directed through region 138 (seeFIG. 2A).

Overview of a Long Segment Ultrasonic Catheter.

FIGS. 3A and 3B illustrate one embodiment of an ultrasonic catheter 10,which is particularly well-suited for treating long segment peripheralarterial occlusions, such as those occasionally found in the arteries ofthe leg.

As illustrated in FIG. 3A, the ultrasonic catheter 10 generallycomprises a multi-component tubular body 12 having a proximal end 14 anda distal end 15. The tubular body 12 and other components of thecatheter 10 can be manufactured in accordance with any of a variety ofconventional catheter manufacturing techniques. Suitable dimensions forthe catheter components can be readily selected based on the natural andanatomical dimensions of the treatment site and of the desiredpercutaneous insertion site.

In an exemplary embodiment, the tubular body 12 is elongate andflexible, and comprises an outer sheath 16. The outer sheath 16preferably includes a support section 17 located at the proximal end andan energy delivery section 18 located at the distal end of the catheter10. In one embodiment, the support section 17 comprises extruded PTFE,PEEK, PE and/or similar materials that provide the outer sheath 16 withenough flexibility, kink resistance, rigidity and structural supportnecessary to push the energy delivery section 18 to a treatment site. Inan embodiment particularly well-suited for treating thrombus in thearteries of the leg, the outer sheath 16 has an outside diameter ofapproximately 0.060 inches to approximately 0.075 inches. In such, anembodiment, the outer sheath 16 has an axial length of approximately 90centimeters.

In an exemplary embodiment, the energy delivery section 18 of the outersheath 16 comprises a relatively thin material compared to the supportsection 17. A thinner material advantageously increases the acoustictransparency of the energy delivery section 18. Suitable materials forthe energy delivery section 18 include, but are not limited to, high orlow density polyethylenes, urethanes, nylons, and so forth.

Referring now to the exemplary embodiments illustrated in FIGS. 3A and3C, the outer sheath 16 defines a utility lumen 28 that extends throughthe length of the catheter 10. In the exemplary embodiment illustratedin FIG. 3A, the utility lumen 28 has a distal exit port 29 and aproximal access port 31. The proximal access port 31 is defined by abackend hub 33, which is attached to the proximal end of the outersheath 16.

Still referring to FIG. 3A, a delivery lumen 30 is positioned adjacentthe energy delivery section 18. The delivery lumen 30 includes an inletport 32, which is formed in the backend hub 33 and is coupled to atherapeutic compound source via a hub such as a Luer type fitting. Thedelivery lumen 30 can be incorporated into the support section 17 (asillustrated in FIG. 3A) or can be external to the support section (asillustrated in FIG. 3C).

The catheter 10 also includes an elongated inner core 34 (see FIG. 3B)having a proximal end 36 and a distal end 38. An ultrasound radiatingmember 40 is positioned at or near the core distal end 38. Furtherinformation regarding methods and structures for mounting ultrasoundradiating members within the inner core can be found in Applicant'sco-pending U.S. patent application Ser. No. 10/309,388, which is herebyincorporated herein by reference in its entirety. For example, in anexemplary embodiment, a plurality of ultrasound radiating members, suchas the ultrasound radiating members disclosed herein and illustrated inFIGS. 12 through 17, can be mounted within the inner core. In suchembodiments, the ultrasound radiating members can be electricallyconnected in series or in parallel.

The inner core 34 has an outer diameter which permits the inner core 34to be inserted into the utility lumen 28 via the proximal access port31. FIG. 4A illustrates the inner core 34 inserted inside the utilitylumen 28 with an ultrasound radiating member 40 is positioned within theenergy delivery section 18. Suitable outer diameters of the inner core34 include, but are not limited to, between approximately 0.010 inchesand approximately 0.100 inches. Suitable diameters of the utility lumen28 include, but are not limited to between approximately 0.015 inchesand approximately 0.110 inches.

The ultrasound radiating member 40 can be rotated or moved within theenergy delivery section 18 as illustrated by the arrows 52 in FIG. 4A.The ultrasound radiating member 40 can be moved within the energydelivery section 18 by manipulating the inner core proximal end 36 whileholding the backend hub 33 stationary. The inner core 34 is at leastpartially constructed from a material that provides enough structuralsupport to permit movement of the inner core 34 within the outer sheath16 without causing the outer sheath 16 to kink. Suitable materials forthe inner core 34 include, but are not limited to, polyimides,polyesters, polyurethanes, thermoplastics, elastomers, and braided wireswith fiber reinforcement.

As illustrated in FIG. 4A, the outer diameter of the inner core 34 canbe smaller than the inner diameter of the utility lumen 28, therebycreating a cooling fluid lumen 44 between the inner core 34 and theutility lumen 28. A cooling fluid can flow through the cooling fluidlumen 44, past the ultrasound radiating members 40 and through thedistal exit port 29. Cooling fluid can be supplied via a cooling fluidfitting 46 provided on the backend hub 33 shown in FIG. 3A. The coolingfluid flow rate and/or the power to the ultrasound radiating members 40can be adjusted to maintain the temperature of the ultrasound radiatingmember 40 within a specified range.

Referring now to FIG. 4B, the cooling fluid can be flowed from thecooling fluid fitting 46 through the cooling fluid lumen 44 asillustrated by arrows 48. The cooling fluid fitting 46 optionallyincludes a hemostasis valve 50 having an inner diameter thatsubstantially matches the diameter of the inner core 34. The matcheddiameters reduce leaking of the cooling fluid between the cooling fluidfitting 46 and the inner core 34.

Referring now to the exemplary embodiment illustrated in FIG. 4C, theultrasound radiating member 40 comprises a hollow cylinder, and theinner core 34 defines a central lumen 51, which extends through theultrasound radiating member 40. In such embodiments, the cooling fluidflows through the central lumen 51, and past and through the ultrasoundradiating member 40, thereby providing cooling to the ultrasoundradiating member 40. In this configuration, the cooling fluid can besupplied via the proximal access port 31, with the cooling fluid fitting46 and hemostasis valve 50 providing a seal between the inner core 34and the outer sheath 16. In modified embodiments, the sheath 16 can beclosed at the catheter distal end, thereby providing a system forrecirculating cooling fluid, and for preventing cooling fluid fromentering the patient's vascular system.

Referring again to the exemplary embodiment illustrated in FIG. 3A, thecatheter 10 includes an occlusion device 22 positioned at the distal endof the catheter 10. In such embodiments, the utility lumen 28 extendsthrough the occlusion device 22. The portion of the utility lumen 28extending through the occlusion device 22 has a diameter that canaccommodate a guidewire (not shown) but that prevents the ultrasoundradiating member 40 from passing through the occlusion device 22.Suitable inner diameters for the occlusion device 22 include, but arenot limited, to between approximately 0.005 inches and approximately0.050 inches.

Referring now to the exemplary embodiment illustrated in FIG. 5A, thedelivery lumen 30 includes a therapeutic compound delivery portion thatis positioned adjacent the energy delivery section 18. As illustrated inFIG. 5B, in an exemplary embodiment, the delivery lumen 30 is woundaround the tubular body 12 in the energy delivery section 18. In suchembodiments, the delivery lumen 30 includes a series of delivery ports58. A therapeutic compound source coupled to the inlet port 32 canprovide a pressure which drives the therapeutic compound through thedelivery lumen 30 and out the delivery ports 58. A suitable material forthe delivery lumen 30 includes, but is not limited to, high or lowdensity polyethylenes, urethanes, nylons, and so forth.

In modified embodiments, the catheter 10 can include a plurality ofdelivery lumens 30. The delivery lumens 30 can be wound around theenergy delivery section 18 or they can be positioned along the length ofthe energy delivery section 18 as illustrated in FIGS. 5C and 5D. Eachdelivery lumen 30 can be coupled to the same drug inlet port 32, or eachdelivery lumen 30 can be coupled to an independent drug inlet port 32,thus allowing different therapeutic compound solutions to be deliveredto different delivery ports 58.

In an exemplary embodiment, the delivery ports 58 are positioned closeenough to achieve a substantially even flow of therapeutic compoundsolution around the circumference of the energy delivery section 18, andalong the length of the energy delivery section 18. The proximity ofadjacent delivery ports 58 can be changed by changing the density ofdelivery ports 58 along the delivery lumen 30, by changing the number ofwindings of the delivery lumen 30 around the energy delivery section 18,or by changing the number of delivery lumens 30 positioned along theenergy delivery section 18. In one embodiment, the windings of thedelivery lumens 30 has a pitch that ranges from about one spiral per onecentimeter to about one spiral per 20 centimeters.

The size of the delivery ports 58 can be the same or can vary along thelength of the delivery lumen 30. For example, in one embodiment, thesize of the delivery ports 58 along the distal portion of the energydelivery section 18 are larger than the delivery ports 58 along theproximal portion of the energy delivery section 18. The increase in sizeof the delivery ports 58 can be configured to produce similar flow ratesof therapeutic compound solution through each delivery port 58. Asimilar flow rate increases the uniformity of therapeutic compoundsolution flow rate along the length of the outer sheath 16. In oneembodiment in which the delivery ports 58 have similar sizes along thelength of the delivery lumen 30, the delivery ports 58 have a diameterof between approximately 0.0005 inches and approximately to 0.0050inches. In another embodiment in which the size of the delivery ports 58changes along the length of the delivery lumen 30, the delivery ports 58have a diameter of between approximately 0.0001 inches and approximately0.005 inches at the proximal end and between about 0.0005 inches andapproximately 0.020 inches at the distal end. The increase in sizebetween adjacent delivery ports 58 can be substantially uniform betweenalong the delivery lumen 30. The dimensional increase of the deliveryports 58 can be dependent upon the material and the diameter of thedelivery lumen 30. The delivery ports 58 can be punched, drilled, burntwith a laser, and so forth, into the delivery lumen 30.

Uniformity of the drug solution flow along the length of the outersheath 16 can also be increased by increasing the density of thedelivery ports 58 toward the distal end of the delivery lumen 30.Additionally, the delivery ports 58 can be slits with a straight shape(as illustrated in FIG. 5E) or an arcuate shape (as illustrated in FIG.5F). The delivery lumen 30 can be constructed from materials such aspolyimide, nylon, Pebax®, polyurethane or silicon. When the deliverylumen 30 contains drug solution, the slits remain closed until thepressure within the delivery lumen 30 exceeds a threshold pressure,where the pressure on each of the slit-shaped delivery ports 58 isapproximately uniform. Once the threshold pressure is exceeded, theslit-shaped delivery ports 58 will open almost simultaneously, resultingin a nearly uniform flow of therapeutic compound solution from theslits. When the pressure in the delivery lumen 30 falls below thethreshold pressure, the slit-shaped delivery ports 58 close and preventdelivery of additional therapeutic compound solution. Generally, thestiffer the material used to construct the delivery lumen 30, the higherthe threshold pressure at which the slit-shaped delivery ports 58 willopen. The slit shape can also prevent the delivery ports 58 from openingwhen exposed to low pressures from outside the outer sheath 16. As aresult, slit shaped delivery ports 58 can enhance control of therapeuticcompound delivery.

In the embodiment illustrated in FIG. 6A, the outer sheath 16 and energydelivery section 18 are constructed from a single material. Suitablematerials include, but are not limited to, high or low densitypolyethylenes, urethanes, nylons, and so forth. The entire outer sheath16, or only the outer sheath proximal end, can be reinforced bybraiding, mesh or other constructions to increase the ability of thecatheter to be pushed through a patient's vasculature (“pushability”).As illustrated in FIG. 6A, the delivery ports 58 can be incorporatedinto the outer sheath 16. The delivery ports 58 can be coupled withindependent delivery lumens 30 formed within the outer sheath 16, asillustrated in FIG. 6B.

In the exemplary embodiment illustrated in FIG. 7, the outer sheath 16includes a support section 17 that is constructed from a differentmaterial than the energy delivery section 18. As mentioned above, theenergy delivery section 18 can be constructed from a material whichreadily transmits ultrasound energy. The support section 17 can beconstructed from a material which provides structural strength and kinkresistance. Further, the support section 17, or the proximal end of thesupport section 17, can be reinforced by braiding, mesh or otherconstructions to increase kink resistance and pushability. Suitablematerials for the support section 17 include, but are not limited toPTFE, PEEK, PE and/or similar materials. Suitable outer diameters forthe support section 17 include, but are not limited to betweenapproximately 0.020 inches and approximately 0.200 inches. Suitablematerials for the energy delivery section 18 include, but are notlimited to high or low density polyethylenes, urethanes, nylons, andother materials that produce minimal ultrasound attenuation. Suchmaterials readily transmit ultrasound energy with minimal absorption ofthe ultrasound energy. FIG. 7 also illustrates an occlusion device 22that is integrally formed with the energy delivery section 18.

Electrical Specifications.

The foregoing electrical specification relate generally to both smallvessel and long segment ultrasonic catheter. In the exemplaryembodiments disclosed herein, the ultrasound radiating members compriseultrasonic transducers configured to convert, for example, electricalenergy into ultrasonic energy. An exemplary ultrasonic transducer forgenerating ultrasonic energy from electrical energy includes is apiezoelectric ceramic oscillator. In a modified embodiment, theultrasonic energy can be generated by an ultrasonic transducer that isremote from the ultrasound radiating members, and the ultrasonic energycan be transmitted to the ultrasound radiating members via a wire, forexample.

In an exemplary embodiment, the ultrasound radiating members comprise anultrasonic transducer with a cylindrical shape. In other embodiments,the ultrasonic transducer can be a block, a hollow cylinder or a disk.The ultrasound radiating members can optionally be positionedconcentrically around the inner core 34. In a modified embodiment, theultrasound radiating members are formed of an array of smallerultrasound radiating members. Similarly, a single ultrasound radiatingmember can be formed a combination of several smaller ultrasoundradiating members.

As mentioned previously, suitable operating frequencies for theultrasound radiating members include, but are not limited to, from about20 kHz to less than about 20 MHz. In one embodiment, the frequency isbetween about 500 kHz and about 20 MHz, and in another embodiment thefrequency is between about 1 MHz and about 3 MHz. In yet anotherembodiment, the ultrasonic energy has a frequency of about 3 MHz.

In embodiments wherein the catheter includes a plurality of ultrasoundradiating members, ultrasound radiating member can be individuallypowered. For example, in one such embodiment, if the catheter includes nultrasound radiating members, the catheter will also include 2n wires toindividually power n ultrasound radiating members. In other embodiments,the ultrasound radiating members 40 can be electrically coupled inserial or in parallel, as illustrated in FIGS. 8A and 8B. Thesearrangements permit more flexibility as they use fewer wires. Each ofthe ultrasound radiating members can receive power simultaneouslywhether the ultrasound radiating members are in series or in parallel.When the ultrasound radiating members are connected in series, lesscurrent is required to produce the same power from each ultrasoundradiating member than when the ultrasound radiating members areconnected in parallel. The reduced current allows smaller wires to beused to provide power to the ultrasound radiating members, andaccordingly increases the flexibility of the catheter. When theultrasound radiating members are connected in parallel, an ultrasoundradiating member can fracture or otherwise fail without breaking thecurrent flow and interrupting the operation of the other ultrasoundradiating members.

In an exemplary embodiment, the output power of the ultrasound radiatingmembers can be controlled. For example, as illustrated in FIG. 8C, acommon wire 61 can provide power of plurality of ultrasound radiatingmembers 40, while each ultrasound radiating member 40 has its own returnwire 62. A particular ultrasound radiating member 40 can be individuallyactivated by closing a switch 64 to complete a circuit between thecommon wire 61 and the return wire 62 associated with the particularultrasound radiating member 40. Once a switch 64 corresponding to aparticular ultrasound radiating member 40 has been closed, the amount ofpower supplied to the ultrasound radiating member 40 can be adjustedusing a potentiometer 66. Accordingly, a catheter with n ultrasoundradiating members 40 uses only n+1 wires, and still permits independentcontrol of the ultrasound radiating members 40. This reduced number ofwires increases the flexibility of the catheter. To further improve theflexibility of the catheter, the individual return wires 62 can havediameters which are smaller than the common wire 61 diameter. Forinstance, in an embodiment where n ultrasound radiating members arepowered simultaneously, the diameter of the individual return wires 62can be approximately the square root of n times smaller than thediameter of the common wire 61.

As illustrated in the exemplary embodiment illustrated in FIG. 3B, thecatheter further includes one or more temperature sensors 20 located atthe catheter distal end. (The small vessel catheter illustrated in FIG.2B also optionally includes a temperature sensor 136.) In suchembodiments, the inner core proximal end 36 includes a temperaturesensor lead 24, which is operatively connected to the temperaturesensors 20. In the modified embodiment illustrated in FIG. 3C, thetemperature sensors 20 are positioned in the energy delivery section 18on the surface of the outer sheath 16. In such embodiments, thetemperature sensor lead 24 extends from the outer sheath proximal end.Suitable temperature sensors 20 include, but are not limited to,temperature sensing diodes, thermistors, thermocouples, RTDs, and fiberoptic temperature sensors which use thermalchromic liquid crystals.Suitable temperature sensor 20 geometries include, but are not limitedto, a point, patch, a stripe, and a band around the outer sheath 16. Thetemperature sensors 20 can be positioned on the outer sheath 16 or onthe inner core 34 near the ultrasound radiating members 40. In anexemplary embodiment, the temperature sensors 20 are positioned near theenergy delivery section 18.

The temperature sensors 20 can be electrically connected as illustratedin FIG. 9. Each temperature sensor 20 can be coupled with a common wire61 and an individual return wire 62. Accordingly, n+1 wires can be usedto independently sense the temperature at n temperature sensors 20. Thetemperature at a particular temperature sensor 20 can be determined byclosing a switch 64 to complete a circuit that includes the particulartemperature sensor 20. When the temperature sensors 20 arethermocouples, the temperature can be calculated from the voltage in thecircuit using, for example, a sensing circuit 63. To improve theflexibility of the outer sheath 16, the individual return wires 62 canhave diameters which are smaller than the diameter of the common wire61.

Each temperature sensor 20 can also be independently wired. In suchembodiments, n independently wired temperature sensors 20 use 2n wiresalong the outer sheath 16.

The flexibility of the outer sheath 16 and inner core 34 can also beimproved by using fiber optic based temperature sensors 20.Particularly, in such embodiments only n fiber optics are used to sensethe temperature at n temperature sensors 20.

The catheter 10 can be used with a feedback control system 68, asillustrated in FIG. 10. In such embodiments, the temperature at eachtemperature sensor 20 is monitored, and the output power of the energysource 70 is adjusted accordingly. The physician can, if desired,override the closed or open loop system.

In the exemplary embodiment illustrated in FIG. 10, the feedback controlsystem 68 includes an energy source 70, a power circuit 72, and a powercalculation device 74 coupled with the ultrasound radiating members 40.A temperature measurement device 76 is coupled with the temperaturesensors 20 on the outer sheath 16 or the inner core 34. A processingunit 78 is coupled with the power calculation device 74, the powercircuits 72, and a user interface and display 80.

In operation, the temperature at the temperature sensors 20 isdetermined at the temperature measurement device 76. The processing unit78 receives the determined temperatures from the temperature measurementdevice 76. The determined temperatures can then be displayed to the userat the user interface and display 80.

The processing unit 78 includes logic for generating a temperaturecontrol signal. The temperature control signal is proportional to thedifference between the measured temperature and a desired temperature.The desired temperature can be determined by the user or be presetwithin the processing unit 78. For example, in an exemplary embodiment,the user sets the desired temperature using the user interface anddisplay 80.

The temperature control signal is received by the power circuit 72. Thepower circuit 72 can be configured to adjust the power level, voltage,phase and/or current of the energy supplied to the ultrasound radiatingmembers 40 from the energy source 70. For instance, when the temperaturecontrol signal is above a particular level, the power supplied to aparticular ultrasound radiating member 40 can be reduced in response tothe temperature control signal. Similarly, when the temperature controlsignal is below a particular level, the power supplied to a particularultrasound radiating member 40 can be increased in response to themagnitude of the temperature control signal. After each poweradjustment, the processing unit 78 monitors the temperature sensors 20and produces another temperature control signal which is received by thepower circuits 72.

The processing unit 78 can also include safety control logic. The safetycontrol logic detects when the temperature at a temperature sensor 20has exceeded a safety threshold. The processing unit 78 can then providea temperature control signal which causes the power circuit 72 to reduceor stop the delivery of energy from the energy source 70 to theultrasound radiating members 40.

Because the ultrasound radiating members 40 can move relative to thetemperature sensors 20 in certain embodiments, it can be unclear whichultrasound radiating member should have a power, voltage, phase and/orcurrent level adjustment. Consequently, each ultrasound radiating member40 is identically adjusted in one embodiment. In a modified arrangement,the power, voltage, phase, and/or current supplied to each of theultrasound radiating members 40 is adjusted in response to thetemperature sensor 20 which indicates the highest temperature. Makingvoltage, phase and/or current adjustments in response to the temperatureof the temperature sensor 20 indicating the highest temperature canreduce the likelihood that the treatment site overheats.

The processing unit 78 can be configured to receive a power signal fromthe power calculation device 74. The power signal can be used todetermine the power being received by each ultrasound radiating member40. The determined power can then be displayed to the user on the userinterface and display 80.

The feedback control system 68 can maintain the treatment site within adesired temperature range. For example, to prevent the temperature ofthe treatment site from increasing more than 6° C. above bodytemperature, and thus causing tissue damage, the ultrasound radiatingmembers 40 can be independently monitored and controlled as describedabove. In one embodiment, the processing unit 78 can be preprogrammed todrive each ultrasound radiating member 40 at a predetermined energy fora predetermined length of time.

The processing unit 78 can comprise a digital or analog controller, or acomputer with software. In embodiments wherein the processing unit 78 isa computer, it can include a central processing unit coupled through asystem bus. The user interface and display 80 can comprise a mouse,keyboard, a disk drive or other non-volatile memory system, a displaymonitor, and other peripherals. Program memory and data memory can alsobe coupled to the bus.

In lieu of the series of power adjustments described above, a profile ofthe power to be delivered to each ultrasound radiating member 40 can beincorporated in the processing unit 78. A preset amount of energy to bedelivered can also be profiled. The power delivered to each ultrasoundradiating member 40 can the be adjusted according to the profiles.

Methods of Use.

FIGS. 11A through 11G illustrate an exemplary method for using theultrasonic catheter 10. This method is applicable to both long segmentand small vessel catheters. In FIG. 11A, a guidewire 84 similar to aguidewire used in typical angioplasty procedures is directed throughvessels 86 toward a treatment site 88 which includes a clot 90. Theguidewire 84 is optionally directed through the clot 90. Suitablevessels include, but are not limited to, the large periphery bloodvessels of the body. Of course, as mentioned above, the ultrasoniccatheter 10 can also be used for various imaging applications and fortreating and/or diagnosing other diseases in other body parts.

In FIG. 11B, the outer sheath 16 is advanced over the guidewire 84 usingover-the-guidewire techniques. The outer sheath 16 is advanced until theenergy delivery section 18 is positioned at the clot 90. Radiopaquemarkers are optionally positioned at the energy delivery section 18 ofthe outer sheath 16 to aid in the positioning of the outer sheath 16within the treatment site 88.

Referring now to FIG. 11C, the guidewire 84 is withdrawn from theutility lumen 28 by pulling the guidewire 84 proximally while holdingthe outer sheath 16 stationary.

In FIG. 11D, a temperature monitor 92 is coupled with the temperaturesensor leads 24, a cooling fluid source 94 is coupled with the coolingfluid fitting 46, and a therapeutic compound solution source 96 iscoupled with the inlet port 32. The therapeutic compound solution source96 can be a syringe with a Luer fitting that is complementary to theinlet port 32. Pressure can be applied to a plunger 98 on thetherapeutic compound solution source 96, thereby driving the therapeuticcompound through the delivery lumen 30. The therapeutic compound isdelivered from the delivery lumen 30 through the delivery ports 58 asillustrated by the arrows 99 in FIG. 11E. Suitable therapeutic compoundsinclude, but are not limited to, an aqueous solution containing athrombolytic agent (that is, a clot-dissolving drug), such as, heparin,urokinase, streptokinase, TPA and BB-10153. In other embodiments,wherein the ultrasonic catheter is not used to remove a thrombus, othertherapeutic compounds (such as cancer treating drugs, genetic material,light activated drugs and so forth) can be delivered through thedelivery lumen.

Referring now to FIG. 11F, in embodiments wherein the ultrasoundradiating member 40 is movable with respect to the utility lumen 28, theinner core 34 is inserted into the utility lumen 28 until the ultrasoundradiating member 40 is positioned within the energy delivery section 18.To aid in positioning the ultrasound radiating member 40, radiopaquemarkers can be affixed to the inner core 34 adjacent the ultrasoundradiating members 40, or the ultrasound radiating members 40 themselvescan be radiopaque. In a modified embodiment, the ultrasonic energyradiated by the ultrasound radiating members 40 can be used to aidplacement. Once the inner core 34 is properly positioned, the ultrasoundradiating member 40 is activated to deliver ultrasonic energy throughthe energy delivery section 18 to the clot 90. In one embodiment, theultrasonic energy has a frequency between approximately 20 kHz andapproximately 20 MHz. In another embodiment, the frequency is betweenabout 500 kHz and about 20 MHz. In another embodiment, the frequency isbetween about 1 MHz and about 3 MHz. In another embodiment, thefrequency is about 3 MHz. While the ultrasonic energy is beingdelivered, the ultrasound radiating member 40 can optionally be movedwithin the energy delivery section 18 as illustrated by the arrows 52.The ultrasound radiating member 40 can be moved within the energydelivery section 18 by manipulating the inner core proximal end 36 whileholding the backend hub 33 stationary. In the illustrated embodiment, acooling fluid flows through the cooling fluid lumen 44 and out theocclusion device 22.

The cooling fluid can be delivered before, after, during orintermittently with the delivery of the ultrasonic energy. Similarly,the therapeutic compound can be delivered before, after, during orintermittently with the delivery of ultrasonic energy. As a result, theacts illustrated in FIGS. 11A through 11F can be performed in differentorders than are described above. The therapeutic compound and energy areapplied until the clot 90 is partially or entirely dissolved, asillustrated in FIG. 11G. Once the clot 90 has been sufficientlydissolved, the outer sheath 16 and inner core 34 are withdrawn from thetreatment site 88.

Further information regarding other techniques for treating a clot usingultrasonic energy delivered from a catheter can be found in Applicant'sco-pending U.S. patent application Ser. No. 09/107,078, which is herebyincorporated herein by reference in its entirety.

Ultrasound Radiating Members: Structures.

A wide variety of ultrasound radiating member configurations can be usedwith the catheters described above. As evident from the foregoingdescription, in certain embodiments the ultrasound radiating memberscomprise an elongate cylinder of piezoelectric material having a hollowcore through which materials such as a cooling fluid, a therapeuticcompound, or electrical conductors can be passed. Such ultrasoundradiating member embodiments can be used with both long segment andsmall vessel ultrasonic catheters.

Exemplary embodiments of an ultrasound radiating member 200 areillustrated in FIGS. 12A through 12E. In these embodiments, theultrasound radiating member 200 comprises a front face 202, a rear face(not shown) that is opposite the front face, and a hollow central core204 that extends along the longitudinal axis of the ultrasound radiatingmember 200. In such embodiments, the front and rear faces form ann-sided polygon. For example, in FIG. 12A, the front and rear faces havefive sides and form a pentagon. In FIG. 12B, the front and rear faceshave six sides and form a hexagon. In FIG. 12C, the front and rear faceshave eight sides and form an octagon. In FIG. 12D, the front and rearfaces have three sides and form a triangle. In FIG. 12E, the front andrear faces have four sides and form a square. In these embodiments, thesides of the front and rear faces are connected by generally rectangularside faces 206, which together form the outer surface of the ultrasoundradiating member 200.

As described herein, in an exemplary embodiment the ultrasound radiatingmember 200 comprises a piezoelectric ceramic or a similar material. Inone embodiment, illustrated in FIG. 13, the side faces 206 and thecentral core 204 are coated with a conductive material. The conductivematerial can be applied using an appropriate application technique, suchas electroplating. A first wire 208 is attached to the central core 204,and a second wire 210 is connected to at least one of the side faces206. In such embodiments, application of a voltage difference 212 acrossthe first and second wires causes the ultrasound radiating member 200 togenerate ultrasonic energy.

In a modified embodiment, the ultrasound radiating member 200 is mounteddirectly on an elongate member that extends through the central core204. This configuration is particularly advantageous in applicationswhere a plurality of ultrasound radiating members are to be mountedwithin the inner core 34, as disclosed herein and as illustrated inFIGS. 3B and 4A. The ultrasound radiating members can be electricallyconnected in series or in parallel. For example, in an embodimentwherein the ultrasound radiating members are electrically connected inparallel, a common wire runs through, and is electrically connected to,the centers of several ultrasound radiating members, and a second wireruns along, and is electrically connected to, the side faces of theultrasound radiating members. In an embodiment wherein the ultrasoundradiating members are electrically connected in series, an electricallyinsulating core runs through the centers of several ultrasound radiatingmembers, and a wire connects the inner electrode and the outer electrodeof adjacent ultrasound radiating members. In still other embodiments,the ultrasound radiating members can be electrically grouped, such thata separate groups of ultrasound radiating members can be individuallyactivated.

The embodiments disclosed herein advantageously allow a plurality ofultrasound radiating members to be mounted within an inner core 34 thatis configured to be inserted into the tubular body of an ultrasoniccatheter. The ultrasound radiating members illustrated in FIGS. 12Athrough 12E are particularly well suited for such applications, becausestructural members, electrical members, and/or fluids can be passedthrough the central core 204.

The ultrasound radiating members 200 illustrated in FIGS. 12A through12E have several advantages. For example, such ultrasound radiatingmembers 200 have more radiating faces and thus produce a more radiallyuniform distribution of ultrasound energy as compared to a rectangularblock or flat plate. Moreover, as compared to cylindrical ultrasoundmembers, the ultrasound radiating members 200 described herein have alarger output region and have lower mechanical stresses duringoperation. Lower mechanical stresses during operation result in lowerfailure rates.

Although not illustrated, modified embodiments of the ultrasoundradiating members 200 have side faces 206 that are non-rectangular (forexample, square or tapered) and/or not identical.

Ultrasound Radiating Members: Manufacturing Techniques.

Improved methods for manufacturing ultrasound radiating members,including the ultrasound radiating members illustrated in FIGS. 12Athrough 12E are described herein.

As illustrated in FIG. 14, a sheet 214 of piezoelectric ceramic orsimilar material is provided. In an exemplary embodiment, the sheet 214has a thickness t that is greater than the length of the finishedultrasound radiating member. A plurality of holes 216 are then drilledinto the sheet 214. In an exemplary embodiment, the holes 216 aredrilled in a uniform pattern. In one embodiment, the holes 216 arethrough holes, which extend through the sheet 214. In anotherembodiment, the holes 216 are blind holes that do not extend through thesheet 214. In exemplary embodiments wherein the holes 216 are blindhoes, the blind holes are drilled to a depth that is greater than thelength of the finished ultrasound radiating member.

Referring now to FIGS. 15A and 15B, in an exemplary embodiment, theperforated sheet 214 is then diced with a dicing blade or otherprecision cutting tool to produce an n-sided polygonal geometry. Forexample, in FIG. 15A, a pattern of cuts 218 are used to produce ahexagonal ultrasound radiating member 220 centered about each hole 216.In FIG. 15B, the pattern of cuts 218 produces an octagonal ultrasoundradiating member 222 that is centered about each hole 216. In otherembodiments, the cuts 218 can be arranged to form other polygons withmore or fewer sides, such as, triangles, squares, and pentagons. Thetriangular geometry, illustrated in FIG. 12D, is particularlyadvantageous because it requires a minimum number of cuts whileproducing no wasted piezoelectric material.

In an exemplary embodiment, the cuts 218 do not extend through thepiezoelectric sheet 214. However, in other embodiments, the cuts 218 doextend through the piezoelectric sheet 214. For example, as illustratedin FIG. 16, in a first region 226, the cuts 218 extend through thepiezoelectric sheet 214; in a second region 228, the cuts 218 do notextend through the piezoelectric sheet 214. In embodiments wherein thecuts 218 do not extend through the piezoelectric sheet 214, the holes216 (illustrated in FIG. 14) can be drilled deeper than the cuts 218.

Still referring to FIG. 16, after the cuts 218 are made, the uppersurface of the sheet, which includes the interior surfaces of the holes216 and the interior surfaces of the cuts 218, are plated with aconductive coating. This plating process provides a conductive coatingon the central core 204 and the side faces 206 of the ultrasoundradiating members to be harvested from the piezoelectric sheet. In suchembodiments, plating material deposited on the top surface 224 of thesheet (that is, on the front or rear faces of the ultrasound radiatingmembers 200) can be removed using a grinding wheel 230, by milling, orusing other methods (for example, by grit blasting).

Referring now to FIG. 17, in an exemplary embodiment, the individualultrasound radiating members are harvested by using a dicing blade 232or other precision cutting tool to separate uncut backside material 234from the cut ultrasound radiating members 200. In one embodiment,illustrated in FIG. 17, the dicing blade 232 cuts at an angle that issubstantially perpendicular to the longitudinal axis of the holes 216.In the exemplary embodiment illustrated in FIG. 17, the sheet 214 isplaced upright, and is cut vertically downward, such that the cutultrasound radiating members 200 can be caught and removed without beingdamaged by the dicing blade 232. In such embodiments, the dicing bladecut intersects the cuts 218 and the holes 216, thereby producingfinished ultrasound radiating members as illustrated in FIGS. 12Athrough 12E.

The methods for manufacturing ultrasound radiating members disclosedherein have several advantages. For example, ultrasound radiatingmembers having the configurations disclosed herein subject thepiezoelectric material to reduced mechanical stresses during use, whichdecreases the likelihood of fracture and grain disruption as compared toconventionally manufactured ultrasound radiating members. Furthermore,the polygonal ultrasound radiating members described herein emitultrasonic energy around a larger effective area, and with an improvedoutput pattern, as compared to conventional cylindrical ultrasoundradiating members. The methods disclosed herein are also less complexand less expensive than conventional machining methods. These methodsare also particularly useful for manufacturing miniaturized ultrasonicelements.

SCOPE OF THE INVENTION

While the foregoing detailed description discloses several embodimentsof the present invention, it should be understood that this disclosureis illustrative only and is not limiting of the present invention. Itshould be appreciated that the specific configurations and operationsdisclosed can differ from those described above, and that the methodsdescribed herein can be used to manufacture non-piezoelectriccomponents, and yet remain within the scope of the present invention.Thus, the present invention is to be limited only by the followingclaims.

1. A method comprising: providing a substantially planar slab of piezoelectric material having a top surface; drilling a plurality of holes through the top surface and into the substantially planar slab; making a plurality of cuts through the top surface and into the substantially planar slab, the cuts forming a plurality of polygons that are generally centered about one of the holes; plating the substantially planar slab with an electrically conductive material; removing the electrically conductive material from the top surface of the substantially planar slab; cutting the substantially planar slab substantially parallel to the top surface to separate individual elongate piezoelectric polygons from the slab; and positioning at least one of the elongate piezoelectric polygons within a tubular catheter body.
 2. The method of claim 1, wherein a plurality of elongate piezoelectric polygons are positioned within the tubular catheter body.
 3. The method of claim 2, further comprising electrically connecting the elongate piezoelectric polygons in series.
 4. The method of claim 2, further comprising electrically connecting the elongate piezoelectric polygons in parallel.
 5. The method of claim 1, wherein the holes are drilled through the substantially planar slab.
 6. The method of claim 1, wherein the polygons are pentagons.
 7. The method of claim 1, wherein the polygons are triangles. 